As a society becomes more industrialized and its citizens attain a higher standard of living, there is a rapid increase in the quantity of disposable refuse. As a consequence, the refuse collection industry is undergoing rapid growth in industrialized countries.
In the collection of refuse, the refuse is compacted within a storage body to densify the refuse and to make it easier to transport, etc. The refuse is, thus, initially dumped into a loading hopper and is then swept from the hopper by the movement of a packing mechanism which sweeps through the hopper. As the packing mechanism sweeps through the hopper, the refuse may be moved from the hopper into a passage leading to a refuse storage body.
In an initially empty condition, a refuse storage body will have an initial volume which is greater than the volume refuse being moved into the storage body from a loading hopper. Thus, refuse which is initially moved into the storage body will be relatively uncompacted while refuse that is moved into the storage body when the storage body is essentially full will be highly compacted. This will produce a non-uniform density of refuse within the storage body as the storage body is filled with the storage body, thus, not containing its full capacity of refuse.
To prevent non-uniform compaction of refuse within a storage body, it is common practice to mount a movable compaction panel within the storage body with the refuse being packed against the compaction panel. When the refuse storage body is empty, the compaction panel is moved to a position adjacent the passage leading into the storage body to reduce the available volume of the storage body. Refuse which is received from the loading hopper is then packed against the compaction panel. When sufficient refuse has been packed against the compaction panel to provide a given densification of the refuse, as indicated by the total force exerted by the refuse against the compaction panel, the compaction panel is then moved a slight distance in a direction leading away from the passage into the storage body. This provides an increase in the effective volume of the refuse storage body and additional refuse is then moved into the storage body and packed against the compaction panel. Packing is continued until the refuse within the storage body again attains a given density as measured by the force exerted against the compaction panel by the refuse. At this point, the compaction panel is again moved to incrementally increase the effective volume of the refuse storage body. By, thus, moving the compaction panel in small increments to incrementally increase the volume of the refuse storage body, the refuse is compacted uniformly as the storage body is progressively filled. This continues until the compaction panel has moved to its forward-most position within the storage body and the storage body is filled with refuse.
In moving a compaction panel within a storage body to provide uniform densification of the refuse as it is packed into the storage body, the compaction panel may be supported within the storage body by means of a telescoping hydraulic cylinder. With the telescoping cylinder in an extended position, the compaction panel is positioned adjacent the point where refuse enters the storage body. As the storage body is progressively filled with refuse and the compaction panel is moved forwardly in small increments, the telescoping cylinder may be proressively contracted until the cylinder is completely contracted with the compaction panel in its forwardmost position.
In discharging refuse from a refuse storage body after the body has been filled, the loading hopper and its associated packing mechanism may be pivotally mounted, in the form of a tailgate or like structure, with respect to the refuse storage body. The loading hopper and associated mechanism may, then, be pivoted away from the refuse storage body to provide an opening from the storage body for discharging refuse therefrom. With the loading hopper pivoted to provide an opening in the storage body, refuse may then be discharged by moving the compaction panel in a rearward direction toward the opening in the storage body to push the refuse from the storage body through the opening.
In a refuse packer, as described, the packing mechanism associated with the loading hopper is capable of producing a very large compaction force to density refuse as it is packed against the compaction panel within the refuse storage body. In previous refuse packers, the packing mechanism has generally been rotatably mounted with the packing mechanism undergoing full rotational movement during a single packing cycle. Thus, the packing mechanism in previous packers has been rotated to sweep refuse from a loading hopper during the power stroke of the packing mechanism with the packing mechanism being rotated forwardly and downwardly to a forward position with the hopper. The packing mechanism has then been rotated upwardly and rearwardly during the rearward movement of the packing mechanism.
The described complex movement of the packing mechanism in previous packers during a complete packing cycle has provided a packing movement that is relatively slow since considerable time may be lost during the upward and rearward rotation of the packing mechanism. It would, thus, be desirable if a packing mechanism could be provided which had a less complex movement so that less time would be lost in the movement of the packing mechanism throughout a complete packing cycle.
During the movement of a refuse packing mechanism through a complete packing cycle within a loading hopper, the demands on the packing mechanism will vary. As the packing mechanism begins the power stroke in sweeping refuse from the loading hopper, the powder demands on the packing mechanism are generally relatively low since the refuse being contacted may be in a loose uncompacted state. However, near the end of the power stroke there is generally a sharp increase in the power demands on the packing mechanism. At this point in the packing cycle, the refuse is no longer in a loose uncompacted state but, rather, is highly compacted as it is densified by forcing it against the compaction panel within the refuse storage body. After the refuse has been compacted against the compaction panel, the packing mechanism is then returned to its rest position generally through upward and rearward rotation within the loading hopper. During this portion of the packing cycle, the power demands on the packing mechanism are relatively slight since the packing mechanism is not working against the reaction force supplied by the densified refuse.
In meeting the varied demands on the packing mechanism, previous refuse packers have generally used a complex hydraulic control system coupled with hydraulic cylinders or motor means to move the packing mechanism through a complete cycle. During the initial movement of the packing mechanism in sweeping refuse from a loading hopper, it has been desirable to move the packing mechanism at a relatively high speed to reduce the time of the packing cycle. In accomplishing this result, the hydraulic control system for the packing mechanism generally functioned to supply a large volume of relatively low pressure hydraulic fluid to the motor means to provide a quick movement of the packing mechanism. Subsequently, when considerable resistance was encountered due to the reaction force of the compacted refuse, the hydraulic control system then functioned to increase the pressure of the hydraulic fluid fed to the motor means while additionally reducing the volume of this fluid. This decreased the speed of the packing mechanism while increasing the force which the packing mechanism applied against the refuse.
After completion of the power stroke of the packing mechanism, the hydraulic control means then functioned to again supply a large volume of relatively low pressure hydraulic fluid to the motor means. This provided a rapid upward and rearward rotation of the packing mechanism to its return position with the packing mechanism in position to begin a new power stroke.
In supplying the varied needs of a refuse packing mechanism during the various portions of a packing cycle, the hydraulic control systems have been relatively complex. This has increased the overall cost of the refuse packer. Also, the complexities of the hydraulic control systems have reduced the reliability of the refuse packers since reliability varies inversely with respect to complexity.
Another disadvantage of the previously used complex hydraulic control systems has been their need for hydraulic fluid whose flow rate and pressure must be varied during the packing cycle. To supply such varying needs of volume flow rate and pressure, it has previously been necessary to use a complex pumping arrangement which is capable of supplying either a high volume of a low pressure fluid or a low volume of a high pressure fluid. Further, the varying demands of a pump system in supplying a varying volume and varying pressure of hydraulic fluid has created problems by imposing diverse requirements upon the engine or motor that is used to operate the pump system. For example, if the pump used to supply hydraulic fluid for operation of the packing mechanism were driven by a truck engine (as in the case of a garbage truck), the truck engine may stall while attempting to power the pump in supplying high pressure fluid. Conversely, during the portions of the packing cycle which require a relatively large volume of hydraulic fluid, the truck engine may produce excessive noise from operating at a higher speed.
In view of the aforementioned difficulties resulting from complex hydraulic control systems and complex pumping arrangements as required for refuse packing mechanisms, it would be desirable if a packing mechanism could be devised which would satisfy the varying needs of the packing mechanism without requiring a complex hydraulic control system or a complex pump and engine combination. Moreover, it would be desirable to have a refuse packing mechanism which would operate satisfactorily from hydraulic fluid of a substantially constant flow rate and a substantially constant pressure. This would, then, eliminate the noise problem that may result when an engine must be operated at a high speed to operate the pump during a portion of the packing cycle.